Gas in oil (making oil)

[MistahBiz]

So quick back story, my engine was fully submerged in freshwater. I pulled sparks so no hydrolock. Drained oil and replaced filter. Rinsed 5 times with oil .until all water was gone. New sparks and she's been running great. Since the submerging all summer I have done a lot of trolling and down rigging for kokanee..this is where my problems arise. Gas in my oil..I decided to try my jet pump which has kept my speed perfectly for downrigging..I put say 40 hrs on that be4 I switched back to prop. I read up on making oil and so I decided to change oil more frequently about 30 hrs..so 3 times since July 2016. Then I started WOT be4 trolling and after. Still having issues, although the boat is running great! More forum research led me to possible torn diaphragm in my fuel pump. 1 and 2 spark plugs have grey soote on them. 3 and 4 sparks look absolutely perfect.. this led me to my fellow boaters..help !!

2003 90 hp 4 stroke with carbs..not efi

 

[Texasmark]

Wouldn't expect 4 strokes to load up trolling like 2 strokers due to the lack of oil in the fuel. However, having a fair amount of higher speed running would tend to keep the engine combustion chambers flushed out including the exhaust scavenging improvement with the lower unit moving at a greater speed creating a vacuum behind the prop to suck on exhaust gasses that you don't get while trolling.

Certainly wouldn't hurt to check diaphragm and with that age and ethanol fuel wouldn't hurt to change it......I just last week was working on a string trimmer (Weedeater) and had a fuel pump problem in that the diaphragm was no longer supple whereby it couldn't vibrate with changes in crankcase pressures and as result it couldn't pump enough fuel to keep the thing running. However, your comments about running great otherwise to me, nullifies suspected problems with your fuel pump.

Excessive fuel could just be from incomplete combustion occurring at low speeds and fuel puddling as a result. Back in the '60's Mercury tilted the design of their fisherman series of motors forward, forcing the cylinders to be higher at the rear, forcing puddled fuel to exit the engine.

I like your idea of running at high speed before and after your trolling. You might consider a higher heat range plug to help it to burn off contaminants as long as you don't get pre ignition at higher speeds (course upping your octane could mitigate that). The other thought is to keep Sea Foam in your fuel. I learned of it on this site when I joined and ran it in the engine I had at the time for over 10 years. Kept the engine spotless, both combustion chambers and fuel system. Can recommends adding 1 oz per gallon (normal engine usage) to your fuel but with what you are doing you might up the quantity to twice that or so. Most auto stores carry it....WW has it for about $6.50 a pint.

 

[MistahBiz]

Thanks Texasmark for your time and info. I'm planning on checking the fuel pump today..I bought a seloc book on my engine, I'm going to do a vacuum test on the diaphragm. This is what concerns me though after my last oil change I pretty much only had it wide open throttle as I am bass fishing now so from spot to spot no more trolling. So I'm still getting an overabundance of gas in my oil. I'm going to check this diaphragm issue and then change my oil and then go out and fish. Also to your remedy of using seafoam I have been using that as well. I will look into possible higher temp spark plugs? Again thanks for your time.

 

[Silvertip]

Making oil on a four stroke occurs due to the following: 1) engine running too cool, 2) wrong prop for how you run the boat. (e.g., even trolling requires a prop that gets the revs up a bit) 3) prolonged slow speed operation 4) ruptured fuel pump diaphram (or fuel pressure regulator diaphram on an injected engine).

 

[MistahBiz]

Thanks for the info Silvertip so I just checked my fuel pump on the tanks side and the motor side both hold pressure properly so I'm back to square one. Yes I did do a lot of trolling so the prolonged speed I did do but like I stated I haven't trolled for the last three trips just up and go bass fishing. As far as the correct prop I worked at Phil's propeller if any of you have heard of it and I have the right prop on the boat. So maybe my engine is not getting warm enough how would I check that is it a thermostat? Here is a couple pics of my vacuum tester hooked up to my Mikuni fuel pump. Thanks for the help guys we're getting there! It won't let me send my pics says there too big not sure how to make them smaller.

 

[MistahBiz]

So I had the wrong enricheners in ( tohatsu) I just purchased the right ones from iboats and Crowley marine (mercury) ..I had a slight miss on idle and my local shop fattened up I guess made it richer ...could this be why I have gas.in my oil. I'm hoping this part change and a Link and sync will get rid of my issue...any thoughts?

 

[ondarvr]

It could be, the most common reason for "making oil" is the motor running too cool though. Bad thermostats are the frequent culprit, some people even put higher temp thermostats in their 4 strokes if they plan to run them at low RPM's for extended periods of time. The richer jetting will just make the issue worse.

 

[MistahBiz]

Thanks for the quick response @ondarvr.. I just swapped the enricheners out getting ready to hook up earmuffs and run it (this is b4 carb tuning..they are still fattened up from the previous enricheners) hoping it runs still! How can I check the possible thermostat issue? Thanks a bunch!

 

[ondarvr]

If you don't know how old the thermostat is just replace it, you could pull it out and check it in a pan of water on the stove, but at that point you've already done all the work.

 

[MistahBiz]

Thanks again ondarvr the engine started and ran smoothly for about 5 min..one Min at the 1000rpm idle then 3000 rpms for about 3 min..then back to idle..I've had motor since 2011 so it's at least that old..I am fishing tomorrow on Shasta lake..I don't know of any other way to check to see if I get gas in oil then to run it for a day..it's got fresh oil and filter in it..it's only ran on this oil for the test today..
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